Caffeine boosts blood pressure

"I just thought it was bad on your skin," he said, touching bumps on his face outside Mom and Pop's Convenience Store on Broad Street.

But the real damage may be deeper.

For black male adolescents such as Lorenzo, caffeine in the sodas could cause higher blood pressure, according to a study of Richmond County high school students by the Georgia Prevention Institute at the Medical College of Georgia. It will be published today in the Archives of Pediatric and Adolescent Medicine.

Using a sodium-controlled diet, MCG researchers looked at the students' caffeine consumption and blood pressure. Black males had the highest blood pressures at the highest category of consumption, which was four or more cans of soda a day.

"This is a fairly good-sized difference in the black males," said study co-author Gregory Harshfield, the associate director at the institute. "(It) will take somebody from being borderline hypertensive to being hypertensive."

Whites who consumed the same amount did not have the same overall increase, Dr. Harshfield said. That might be because of different systems for controlling blood pressure, such as one in which hormones cause the kidneys to retain salt and keep blood-fluid levels, and thus keep blood pressure up, Dr. Harshfield said. In previous research, Dr. Harshfield found that black adolescent males with an exaggerated blood pressure response to stress did not shed salt properly.

In a statement issued Monday in response to the study, the National Soft Drink Association said that when there is a blood pressure increase from drinking sodas it was "less than that normally experienced when climbing a flight of stairs."

The group added that those at risk of high blood pressure or who are more sensitive to caffeine should consult their physicians or consider caffeine-free alternatives.

Heavy soda intake also could be pointing to other factors, said Stephen Daniels, a professor of pediatrics and environmental health at Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine.

"It may be a marker for more fast-food, higher-fat, lower-fiber types of diets," said Dr. Daniels, who wrote an accompanying editorial. Caffeine could be a concern because over the past three decades the amount of soda consumed by adolescents has tripled, according to the editorial.

More studies will be needed to clarify what exactly is happening, Dr. Harshfield said. But his study points out yet another problem for schools that provide soda vending machines, which have become a target for those concerned about childhood obesity.

"We also know that many of those products contain caffeine, so this could be an added problem for some of those beverages and snack foods," Dr. Daniels said.

"The soda machines are not bad just because of the obesity (epidemic)," Dr. Harshfield said. "We're actually showing, particularly in a high-risk group, it can increase their casual blood pressure."

It is particularly important to look at children, and ways of preventing things that might start in adolescents, such as hypertension, Dr. Daniels said.

"Children may be more susceptible to some of these things," he said. "If there are other ways by dietary means that we can prevent higher blood pressure, I think that would be a great thing to know about."